Magnetic disk controller which avoids erroneous write operations to ZBR-type magnetic disks upon detection of a next sector mark from the ZBR magnetic disk

Abstract

In a sector mark waiting stage, when a sector mark detecting signal is input to a magnetic disk controller, the magnetic disk controller initiates a write operation of sector data on a magnetic disk. In a non-sector mark waiting state, when a sector mark detecting signal is input to the magnetic disk controller, the magnetic disk controller stops the write operation of sector data upon the magnetic disk being performed.

I claim: 
     
       1. A magnetic disk controller for a ZBR-type magnetic disk by a magnetic head, comprising: a sequencer for generating a sector mark waiting signal and an index waiting signal to wait for an index pulse signal generated from said magnetic disk at every revolution thereof;   a detecting means, connected to said magnetic head, for detecting a sector mark in said magnetic disk to generate a sector mark detecting signal;   a means for generating said index pulse signal;   a first gate circuit, connected to said sequencer, for generating a waiting signal, transmitting it to said first and second gate circuits, when at least one of said sector mark waiting signal and said index waiting signal is generated;   a second gate circuit, connected to said sector mark detecting means and to said index pulse signal generating means, for generating a detecting signal, when at least one of said sector mark detecting signal and said index pulse signal is generated;   a third gate circuit, connected between said first and second gate circuits and said sequencer, for generating an ID read signal and transmitting it to said sequencer, when said waiting signal is generated and said detecting signal is generated; and   a fourth gate circuit, connected between said first and second gate circuits and said sequencer, for generating a stop signal and transmitting it to said sequencer, when said waiting signal is not generated and said detecting signal is generated,   said sequencer performing a write operation of sector data on said magnetic disk when receiving said ID read signal,   said sequencer stopping the write operation of sector data from being performed when receiving said stop signal.   
     
     
       2. A magnetic disk controller as set forth in claim 1, further comprising a latch circuit, connected to said fourth gate circuit, for storing an information indicating whether or not said sequencer has stopped the write operation of sector data. 
     
     
       3. A magnetic disk controller as set forth in claim 1, further comprising a fifth gate circuit having one input connected to said sector mark waiting signal, another input connected to said sector mark detecting signal, and an output connected to said sequencer and generating a passed sector mark detecting signal only when both said sector mark detecting and said sector mark waiting signals are generated. 
     
     
       4. A magnetic disk controller as set forth in claim 1, further comprising a sixth gate circuit having an input connected to said index waiting signal, and another input connected to said index detecting signal, and an output connected to said sequencer and generating a passed index detecting signal only when both said index waiting and index detecting signals are generated. 
     
     
       5. A magnetic disk controller for a ZBR-type magnetic disk, comprising: means for setting a sector mark waiting state;   means for resetting said sector mark waiting state;   means for detecting a sector mark from said magnetic disk;   means for performing a write operation of sector data upon said magnetic disk when said sector mark waiting state is set and a sector mark detecting signal is detected; and   means for stopping said write operation from being performed when said sector mark waiting state is reset and a sector mark detecting signal is detected;   means for setting an index waiting state to wait for an index pulse signal generated from said magnetic disk at every revolution thereof;   means for resetting said index waiting state;   means for detecting said index pulse signal from said magnetic disk;   means for performing a write operation of sector data on said magnetic disk when said index waiting state is set and an index pulse signal is detected; and   means for stopping said write operation from being performed when said index waiting state is reset and an index pulse signal is detected.